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2 lenses compared
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Feb 20, 2010
Dec 4, 2009
 
Zoom lens
Zoom lens
APS-C / DX
APS-C / DX
17–50 mm
17–70 mm
Yes (4 stops claimed)
Yes (4 stops claimed)
Canon EF, Nikon F (DX), Pentax KAF3, Sigma SA Bayonet, Sony/Minolta Alpha DT
Canon EF, Pentax KAF3, Sony/Minolta Alpha, Sigma SA Bayonet, Nikon F (DX)
 
F2.8
F2.8 - F4.0
F22.0
F22.0 - F32.0
No
No
7
7
Rounded diaphragm
rounded diaphragm
 
17
17
13
13
2 FLD glass elements 2 glass mold elements 1 hybrid aspherical lens
1 ELD glass element 1 hybrid aspherical element 2 glass mold elements
 
0.28 m (11.02)
0.22 m (8.66)
0.2×
0.37×
Yes
Yes
Ultrasonic
Ultrasonic
No
No
Internal
Internal
For Pentax mount, AF will not function with DSLR cameras that do not support HSM
AF will not function with Pentax ist* series and K100D DSLR cameras that do not support HSM
Yes
Yes
No
No
No
No
 
565 g (1.25 lb)
520 g (1.15 lb)
84 mm (3.29)
79 mm (3.11)
92 mm (3.62)
89 mm (3.5)
Metal mount
Metal mount
No
No
Rotary (extending)
Rotary (extending)
77 mm
72 mm
Does not rotate on focusing
Does not rotate on focusing
Yes
Yes
No
No